Keying control method and system



Nov. 30, 1943.

Filed Dec.'12, 1940 OUT flwaqa' INVENTOR arrangement for producing from the usual which very often Patented Nov. 30, .1943

2,335,278 KEYING CONTROL METHOD AND SYSTEM Richard A. Hilferty, Baldwin,

Press Wireless, Inc., Chicago,

of Delaware N. Y.,assignor to 111., a corporation Application December 12, 1940, Serial No. 369,812

14 Claims.

This invention relates to signalling systems and more especially to improved keying control I arrangements for such systems.

A principal object is to provide a novel arrangement for producing substantially squaretopped waves for use in telegraph signalling or similar systems.

Another principal object is to provide an improved keying control circuit which is particularly advantageous in autommatic telegraph transmitters especially those of the Morse code type.

Heretofore it has been found necessary to employ polarized relays for converting the fleeting contact of the automatic Morse transmittin signal controller into marking or spacing" impulses of symmetrical proportions. Since the armatures of conventional polarized relays'have considerable 'mass, an appreciable time interval is required for the armature to complete its transit from the marking to the spacing contact and vice versa. This to a certain degree, represents a loss in signalling time.

Accordingly, it is another principal object of this invention to provide a keying control arrange'ment which is substantially inertlaless so far as the beginning and ending of each signal interval is concerned, resulting in more nearly perfect square-topped signalling waves and a considerable increase in possible signal transmission speeds.

A feature of the invention relates to a keying controlling arrangement employing a novel combination of: grid-controlled gas-discharge tube and grid-controlled vacuum tubes.

' Another feature relates to an improved circuit substantially squaretopped envelopes of A. C. waves of magnified amplitude.

Another feature control circuit which can be controlled directly instantaneous contact controller or conventional automatic or tape-controlled telegraph transmitters, whereby intervening plarized relays or other similar electr'o-mechanical vibrators are avoided. As a result of this feature.'the signalling wave shape and time can be improved because the armature transit time is substantially eliminated, and disturbances arise from maladjustment, deterioration or sticking of the usual polarized relay contacts, are avoided.

A further feature relates to an improved keying control circuit employing a tube of the "thyratron" type.

relates to an improved keying A further feature relates to means for generating recurrent and substantially squaretopped envelopes of A. C. waves at a rate determined substantially entirely by a local or distant timing oscillator, by employing a grid-controlled vacuum tube and a grid-controlled gas discharge tube in a balanced or quasi push-pull arrangement.

A still further feature relates to the novel organization, arrangement and relative interconnection of parts which constitute a more efficient keying control arrangement for telegraph signalling systems and the like.

Other features and advantages not specifically enumerated will be apparent after a consideration of the following detailed descriptions and the appended, claims.

While the invention will be described herein in connection with one particular kind of signalling system, it will be understood that in certain of its aspects the invention is applicable to a wide variety of signalling systems or wave impulse control systems. In the drawing, which represents certain specific embodiments,

Fig. 1 is a schematic wiring diagram of an automatic telegraph keying control system embodying features of the invention.

Fig. 2 is a'schematic diagram of a modiflca-.

tion of the keying arrangement of Fig l.

Referring to Fig. l, the device within the dotted rectangle i represents the signal impulse contacts of any well-known form of tape-controlled telegraph transmitter e. g., an automatic Morse ser er. The transmitter includes a .pair of fixed contacts 2, 3, and associated movable contacts l and 5 carried by a grounded swingable arm assembly 6 which is adapted to rock contacts l and I under control of the perforatedtape which is fed through the machine. The contact assembly I is usually referred to in the art as an auto-head."

Contact 2 in the circuit as shown in Fig. l is the"spacing" contact and contact I is the marking" contact. Contact 2 is connected to the control grid! of a five-element vacuum tube 8 which may be a type #42 tube having an electron-emitting cathode 9, a control grid I, a suppressor grid ID, a shield grid II and a plate or anode II. It will be understood that a grid-controlled tube of a greater or smaller number of electrodes may be used. Preferably, the shield grid II is connected directly to the anode causing the tube to have the operating characteristics of a triode, the grid ll being connected directly to the cathode l. The conll trol grid I is connected to the cathode I throulh a bias resistor 13 of approximately 100,000 ohms and a bias battery M. The resistor and battery are so proportioned that when the contacts 2 and. 4 are open, the control grid of tube 8 is negative- 1y biased substantially to plate current cut-ofi.

The marking contact 3 is .connected to the control grid l6 of a grid-controlled gaseous discharge tubeW-H which for. example may be of a type #885 or ofthe thyratron type such that when a predeterminednegative or blocking potential isapplied to grid [6, the tube is blocked against the flow of plate current, but when the said grid has applied thereto a less negative potential, plate current continues to flow independently of the grid potential until the plate. voltage is reduced. When the contacts 3 and 3 1 circuit of tube 28 thus causing amplification of the waves from source 34. The output energy .of' tube 28 is then available at the terminals of v transformer 31.

In the above sequence of operation, resistor 25 serves to limit the amount of current drawn by are open, grid l8 is negatively biassed with-re spect to cathode l8 by mean'sof battery l4 and resistor l5, the latter being of approximately 100,000 ohms. The plate currents of tubes 8 and I! are supplied by a battery of approximately 250 volts in series with a resistor 2| of approximately 50,000 ohms.

I1. and is also connected across the input electrodes. of a vacuum tube 22 which may be oftthe triode .type.- Preferably however, tube 22 is a five-element tube of the type #42 with its control grid 23 connected to the screen grid 24'- through a grid current limiting resistor 25 of approximately 10,000 ohms and with the oathode 26 connected directly to the suppressor grid 21. Thus the voltage-developed across resistor l8 when tube I! is unblocked, impresses a'positive voltage on grids 23 and 24 causing the plate-cathode impedance of tube 22 to drop whereby an efiective' cathode return circuit for vacuum tube 28 is completed. Tube 28 may be of any well-known form of twin-triode output amplifier tube such as a type #6A6. comprising two sets of triode elements, one set comprising the electron-emitting cathode 28, control grid 30 and plate 3|; the other set comprising cathode 29, control grid 32 and plate 33. The source of waves-to be amplified is represented by the numeral 34 and is connected through transformer 35 in balancedrelation to the grids 30, 32. The'midpoint of the secondary winding of transformer 35 is returned to the cathode 29 through the plate-cathode space of tube 28v as mentioned above. The plate current for tube 28 is supplied by battery 36 which may be of approximately 250 volts and is connected in balanced relation to plates 3|, 33, through the midpoint of the primary winding of output transformer 31.

The manner of operation of the system of Fig. 1 is substantially along the following lines. Assume-that the cathodes of the various tubes have been heated to their proper operating temperatures by suitable cathode heating current sources (not shown) and that batteries of the proper potentials are provided as above described, and that arm 6 is rocked to close-marking contacts 3 and 5. Since the arm 8 is directly connected to ground, at the instantof contact, the grid l6 of tube II will. be at ground potential. At the same instant plate current cut-off bias is maintained on the grid I as above described so that tube 8 is ineffective so'long as the marking contacts are closed and the spac ,ing contacts are open. The grid bias of tube H having been removed by the closure of contacts 3 and 5,52. discharge takes place between its f. 35A resistor IQ of approximately 5000 ohms is "connectedin the cathode return circuit of tube and associated circuit elements.

. moved from control grid 1 which the control grid '23 and thus assists in maintaining the screen grid 24 at a potential sufiiciently positive to maintain good conductivity between plate 38 and cathode 26. Consequently, a series of signalling waves will appear in the output transformer 31, the beginning of this series being substantially instantaneously coincident with the closure .of contacts 3 and 5. Marking current therefore continues toflow at an amplitude determined by the amplification factor of tube 28 This flow of marking current will continue even though the arm 6 is rocked to open contacts 3 and 5 and prior to the closure of contacts 2 and 4. Thus with bothsets of contacts open, tube l1 continues to pass plate current and tube 22 continues to'remain conductive to provide the cathode return circuit 28 as above described. When a spacing impulse is received, thus causing contacts 2 and 4 to close, the negative bias is reis connected directly to ground through contacts 2 and 4. Tube 8 immediately passes plate current which flows through resistor 2|. The drop across resistor 2l is therefore increased to a point at which insuflicient anode potential remains on tube 11 to maintain the discharge. Grid 16 therefore regains control of tube II. At this instant the voltage drop across resistor l9 collapses and removes the positive bias from thegrids 23 and 24. The high internal impedance of tube 22 therefore fails to provide an efiective cathode return circuit for tube 28 which thereupon ceases to amplify and thus produces a space" signal. It will be seen therefore, that the actual signals in transformer 31'will consist of substantially square-topped signals or envelopes of A. C. waves whose wave frequency is determined by source 34 and whose amplitude is determined by tube 28.

Instead of employing a mechanically rockab e contact member such as the arm 6 of the autohead I to control the vacuum tube 8 and the thyratron tube", the control maybe effected by a source of timing waves connected to the foriner 40 to the points'2, 3. The remainder of 38 of Fig. 1.

proportioned in magnitude with respect to the the system of Fig. 2 is identical with; that of Fig. l, the. block 4| representing the elements 22 'to The waves from source 3| are so bias battery 14 and resistors l3, I9, that "the grids 'l and I8 are energized alternately,"positively and negatively. The positive half waves applied to grid 1 for-example are of sufiicient amplitude to overcome thenegative bias, thus ous discharge tube,

, gaseous tube below may be located at a remote point. It will be understood of course that the source 39 may generate alternating current waves of sinusoidal form or the source 39 and the transformer 40 may be replaced by any well-known form of square-topped timing waves such as direct current impulses or the like. The wave frequency of the timing source 39 may be in harmonic relation to the frequency of the signalling source 3|.

, If the marking and spacing intervals at the outdischarge tube, said tubes being normally biased to plate current cut-off, means responsive to a said gas tube, by steadily maintainingthe plate put of the. amplifier are required to be symmetrical, then preferably the alternate half cycles of the timing oscillator 39 should likewise be symmetrical.

Various changes and modifications may be narting 'iromthe spirit and scope of the invenion.

What I claim is: I

1.-In a keying control arrangement, a gridcontrolled vacuum tube, a grid-controlled gas discharge tube, the grid of said vacuum tu and the grid of said discharge tube being connected in substantially balanced relation to opposite sides of the signal input circuit, means normally efiective independently of received si nals to bias the grids of said tubes substantially to plate current cut-oil, means to render only said gas tube conductive in response to one kind of signal impulse, and means to render only said vacuum tube conductive in response to a different kind of signal impulse while simultaneously blocking said gas tube, the blocking of said gas tube being maintained under control of the steady conductivity of said vacuum tube.

2. Ina keying control arrangement, a gridcontrolled vacuum tube, a grid-controlled gas discharge tube, the grid of said vacuum tube and the grid of said discharge tube being connected in substantially balanced relation to opposite sides of the signal input circuit, means normally effective independently of received signals to bias the grids of said tubes substantially to plate current cut-ofi', means responsive to marking signals to overcome the cut-off bias on one tube only, and means-responsive to spacing signals to overcome the cut-oil bias on the other tube only, whereby said tubes respond substantially only to transisitons from one kind of signal to the other, and means to maintain' the gas tube steadily blocked under control of the steady plate conductivity of said vacuum tube.

3. In a keying control arrangement, a gridcontrolled vacuum tube, a grid-controlled gasemeansto render said discharge tube conductive only in response to one character of signal, and means responsive to another character of signalto render said vacuum tube conductive and thereby to block said gas tube, by maintaining the plate potential of the potential as longas the .plate circuit of said vacuum tube is conductive.

4. In a keying control arrangement, a gridcontrolled vacuum'tube, a grid-controlled gas its. discharge-maintainin made in the enclosed embodiments without demarking signal and effective only while said vacuum tube is biased to plate current cut-off to render said gas tube conductive, and means responsive to a spacing signal to render said vacuum tube conductive and thereby to block potential of the gas tube below its dischargesustaining value as long as the plate circuit of said vacuum tube is conductive.

5. In a keying control arrangement, a gridcontrolled vacuum tube, a grid-controlled gas tube, means normally biasing the grids of said tubes to plate current cut-off, a pair of. marking and spacing control contacts, one of said contacts being connected to the grid of the vacuum tube and the other of said contacts being connected to the grid of the gas tube, means to apply a bias neutralizing potential only to one of said grids in response to a marking signal, means to a ply a bias neutralizing potential only to the ot of said grids in response to a spacing signal, said vacuum tube being effective while its bias is neutralized to reduce and maintain reduced the plate potential of said gas tube below its discharge-sustaining value to restore control of the said gas tube to its grid only while said vacuum tube grid bias is neutralized.

6. In a keying control arrangement, a gridcontrolled vacuum tube, a grid-controlled gas discharge tube, means normally biasing the grids of said tubes negatively to plate current cut-ofi, a marking contact, a spacing contact, means controlled by a perforated tape or the like to ground the said grids in accordance with marking or spacing signals whereby only one tube becomes conductive for marking and only the other tube becomes conductive for spacing. 7. A keying control arrangement according to claim 6 in which the platepotential for the gas tube is connected in series with a resistor, and the anode-cathode discharge path of said vacuum tube is connected in parallel to said resistor and source.

8. A keying control arrangement according to claim 6 in which said vacuum tube is of the fiveelement type with the screen grid and plate directly connected and with the suppressor and cathode directly connected.

9. In a keying control arrangeme t, a gridcontrolled gas discharge tube normally biased to plate current 'cut-ofi, means responsive to a marking signal to reduce said bias to render said tube conductive, means" including a grid-controlled vacuum tube responsive to a spacing signal to block said gas tube and'to maintain it blocked as long as the uum tube is steadily conductive, and a gridcontrolled amplifier tube controlled by the plate current of said gas tube.

10. In a keyingcontrol arrangement, a gridcontrolled gas discharge tube, a grid-controlled vacuum tube, means responsive to a marking sig-- nal to render said gas tube conductive and thereby to apply a positive bias to the control grid of.

pla'te circuit of saidvact0 the initiation element type wherein the shield grid and control grid are connected together and the suppressor" grid and cathode are connected together.

13. In a keying control arrangement,.a grid-- controlled gas tube, a grid-controlled vacuum tube, a source of reversible signal potentials connected to said grids in substantially balanced re lation, the said grids being normally biased to plate current cut-ofi in the absence of said signal potentials, and an impedance common to the plate circuits of said tubes and responsive to the steady conductivity of said vacuum tube whereby when the vacuum \tube becomes conductive, it causes said gas tube to become non-conductive.

14. A keying control arrangement according to claim 13 in which another impedance is con-' nected in the anode-cathode circuit of the gas tube anda second grid-controlled vacuum tube is connected acrosssaid other impedance whereby the control grid of said other vacuum tube is positively biased only when said gas tubeiis conductive. V 4

RICHARD A; HILFERTY. 

